4: Bioenergetics

Question 1

what is the word and symbol equation for photosynthesis?

Answer 1

water + carbon dioxide -> oxygen + glucose

6H2O + 6CO2 -> 6O2 + C6H12O6

Question 2

what kind of equation is photosynthesis? why?

Answer 2

endothermic reaction - energy is transferred from the environment to the chloroplasts by light

Question 3

what three factors affect rate of photosynethesis?

Answer 3

light, temperature and carbon dioxide

Question 4

how does temperature affect the rate of photosynthesis?

Answer 4

lower the temperature, less kinetic energy particles have, resulting in fewer successful collisions occurring over a period of time; increasing temperature increases kinetic energy of particles, increasing the likelihood of collisions between reactants and enzymes which results in the formation of products;
at higher temperatures, enzymes can be denatured - this reduces the overall rate

Question 5

how does light affect the rate of photosynthesis?

Answer 5

more light a plant receives, faster the rate of photosynthesis - light energy is required for the reaction to take place; this trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now the limiting factor

Question 6

how does CO2 concentration affect the rate of photosynthesis?

Answer 6

more carbon dioxide that is present, the faster the reaction can occur; this trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now the limiting factor

Question 7

how does the amount of chlorophyll affect the rate of Ps?

Answer 7

they contain the pigment chlorophyll which absorbs light energy for photosynthesis; more chloroplasts a plant has, faster the rate of photosynthesis

Question 8

what is inverse square law?

Answer 8

shows the relationship between light intensity and distance - as the distance increases the light intensity decreases. - inversely proportional to each other

Question 9

what is the equation for light intensity?

Answer 9

light intensity = 1/distance squared

Question 10

how can people increase crop yield?

Answer 10

keep plants in a greenhouse - no shades so mx. amount of light, also glass traps heat so temp is not a limiting factor, also makes it easier to protect them from pests and diseases; artificial lights so photosynthesis can occur at night or when there is less sun light; a heater can burn paraffin to release CO2; watering system to keep plants well watered; ventilation so plants don’t get too hot

Question 11

what are the uses of glucose?

Answer 11

respiration; converted into insoluble starch for storage in the stems, leaves and roots; to produce fat or oil for storage (especially in seeds); to produce cellulose, which strengthens the cell wall; combined with nitrate ions to produce amino acids for protein synthesis

Question 12

what kind of reaction is respiration?

Answer 12

exothermic reaction - continuously occurring in living cells; releases energy

Question 13

why do organisms need energy?

Answer 13

chemical reactions - to build larger molecules from smaller molecules; muscle contraction - movement;
keeping warm - maintain constant temp. for enzymes

Question 14

what is the word and symbol equation for aerobic respiration?

Answer 14

glucose + oxygen -> carbon dioxide + water

C6H12O6 + 6O2 -> 6CO2 + 6H2O

Question 15

what is anaerobic respiration? when does it occur?

Answer 15

incomplete breakdown of glucose into lactic acid to release energy; occurs when the body can’t supply enough oxygen for aerobic respiration, e.g. during exercise

Question 16

what is the word and symbol equation for anaerobic respiration?

Answer 16

glucose -> lactic acid (+ less energy released)

Question 17

where does aerobic respiration occur? how has this place adapted to make the reaction more efficient?

Answer 17

mitochondria; has a highly folded inner membrane to provide a large s.a. for the enzymes involved in respiration

Question 18

why is lactic acid produced in anaerobic respiration?

Answer 18

the oxidation of glucose is incomplete so less energy released

Question 19

what is the equation for anaerobic respiration in plants?

Answer 19

glucose -> CO2 + ethanol (+ less energy released)

Question 20

what is anaerobic respiration in plants used for?

Answer 20

in yeast cells it is called fermentation; important in the baking industry (carbon dioxide makes dough rise) and brewing industry (as ethanol = alcohol)

Question 21

why is lactic acid bad?

Answer 21

it causes muscle fatigue - muscles stop contracting efficiently & cramps

Question 22

why does heart rate increase in response to exercise?

Answer 22

to allow blood to be pumped faster to working muscles - blood carries O2 and C6H12O6 which are required for respiration

Question 23

why do arteries supplying blood to muscles dilate in response to exercise?

Answer 23

so more blood can get to and from muscle cells, transporting reactants and products of RESP

Question 24

why does breathing rate increase in response to exercise? why do we cont. to breathe heavily after exercise?

Answer 24

enables more O2 to be used to convert the lactic acid back to glucose; enables faster removal of CO2 - acidic gas, if left this would build up and alter pH, could denature enzymes

Question 25

why does depth of breathing increase in response to exercise?

Answer 25

allows more O2 to be taken in w each breath for respiration and to increase removal of CO2

Question 26

why does body temp. increase in response to exercise?

Answer 26

respiration releases energy, some is lost as heat energy

Question 27

what is oxygen debt?

Answer 27

the amount of extra oxygen needed to react w accumulated lactic acid to remove it

Question 28

where does lactic acid go?

Answer 28

increased blood supply to muscles removes lactic acids and transports it to the lungs, where it is converted back to glucose (oxygen required)

Question 29

what is glycogen? why do we need it?

Answer 29

polymer of glucose for storage; stored in muscle cells and liver; can be converted by muscle cells back to glucose when there is not enough for respiration

Question 30

what is metabolism?

Answer 30

the sum of all the chemical reactions in a cell or the body

Question 31

give examples of metabolic reactions.

Answer 31

respiration; polymerisation of e.g. starch, glycogen, cellulose, lipids/fats; polymerisation in plants of amino acids then proteins; break down of excess protein to urea by liver (filtered by kidneys)

Question 32

what is metabolism rate?

Answer 32

the rate all the chemical reactions in your body occur

Question 33

what factors affect your metabolic rate?

Answer 33

what you have inherited from your parents via genetics; your age; your sex; the proportion of muscle to fat in your body (muscles have a higher metabolic rate)